This invention relates generally to movement detectors and more particular for movement detectors which include devices to shut off fluid flow.
The danger from earthquakes is well known. The ground trembles causing shock waves and movement to be sent from the point of the earthquake. This movement can be extremely severe. The force of a large earthquake can cause catastrophic damage. Buildings may be toppled, roads may buckle and bridges may collapse. Although earthquakes are better known for occurring in the western United States, some of the most severe earthquakes have occurred in the mid-west and even in the northeast.
While the earthquake itself may cause severe damage, the number of lives that can be lost as a result of fire and explosion is far greater. For example, if a resident has natural gas utility, a pipeline enters the home from a main pipeline from the utility company. In the event of an earthquake the regulator at the incoming pipeline may break and cause natural gas to be spewed into the air and generally in the vicinity of the house. If the gas is ignited an explosion can occur causing severe damage and catastrophic injury.
Thus, it is essential to keep the natural gas confined in the pipeline in order to minimize personal injury and property damage. Devices designed to keep natural gas confined to the pipeline had long been available to the general public. However, these devices have been seldom used by the public because they are generally unreliable. The devices are difficult to set so that they go off at the proper time. For example, Sharp, et al., U.S. Pat. No. 3,927,689, discloses an earthquake response safety valve assembly which relies upon pressure from the weight of a ball on a pin. Hansen, U.S. Pat. No. 5,482,074, discloses a safety cut-off device that utilizes a pendulum trigger assembly to keep a spool member in the open position. Simpson, U.S. Pat. No. 5,143,110, discloses a seismic gas shut-off valve in which a piston is suspended by seven steel balls that rest on the angled floor of an upper chamber and extend partially into the groove so that the ridge rests on the balls. Terrones, U.S. Pat. No. 4,535,796, discloses a seismic actuated shut-off valve that utilizes a severable link. These types of devices go off either too easily or not until extreme movement is reached, in which case the catastrophe may have already occurred without the device ever going off. Thus, in the event of an earthquake, which is not catastrophic in nature but which is significant to break a regulator, the devices may fail to go off. Additionally, if the earthquake is so slight that a regulator or pipeline would not be broken, then such devices may go off causing the homeowner to find the devices unreliable. The homeowner would at the very least need to reset the device. However, because of the inconvenience of resetting the device, the homeowner might adjust the setting so that the device is activated only in the event of a catastrophic earthquake.
Additionally, it has been recognized that being able to reset the device is important. Sharp, et al., in U.S. Pat. No. 4,314,120 restructured their device so that it was resettable. Others have also attempted to make the resettable device. For example, in Kiesow, U.S. Pat. No. 4,103,697, a resettable structure is disclosed which incorporates a square groove with a pin needing a precise tolerance in order to work with an alignment means. The length of the shut off plunger must be precise because if it is too short the gas will flow and if it is too long the pin will not align with a square groove on the plunger. This device is expensive to manufacture as a result. Additionally, the square grove may make it difficult for the Kiesow device to activate the plunger and shut off the gas. Another example of an attempt to make a resettable earthquake activated shut off valve is found in Hansen, U.S. Pat. No. 2,054,563. However, in order to reset this device, the gas line must be turned off and then the device can be reset. Furthermore, Greer, U.S. Pat. No. 4,116,209 discloses a shock actuated valve that has a tapered cylindrical valve gate suspended on an actuator pin. To reset the valve, the user must remove the closure from the stowage arm and engaging the retrieval loop in the valve head with a suitably bent wire. Greer, U.S. Pat. No. 4,745,939, is an improvement of Greer's earlier invention. This device has two valves aligned so that the actuator pins are at a 45-degree angle to one another. Each valve has a tether for resetting the valve by lifting the gate back onto the pin. Once activated, these devices are not easily reset.
The above background reveals what is and has been needed for a long time: a movement detector and a shut-off device that can be properly set to go off only if there is a danger of the gas line breaking causing leakage and which is easily adjustable and resettable.